Abstract

3480

Around 200-600 million people in South and Southeastern Asia chew areca. Areca chewing has been linked to the high incidence of oral squamous cell carcinoma (OSCC) in these regions. However, the impact of areca on cellular signaling is not clear. Mitogen-activated protein kinases (MAPKs) superfamilies, consisting of extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinases/stress activated protein kinase (JNK) and p38MAPK together with transcription factor NF-κB are important for cell proliferation, apoptosis or tumorigenesis. In this study, we examined the activation of MAPKs and NF-κB signaling systems in an oral keratinocyte, OECM-1, treated with ripe areca nut extract (ANE). Serum-starvation synchronized OECM-1 treated with 10 or 20 μg/ml ANE for 24 h caused no decrease in cell viability. By 10 μg/ml ANE treatment, an increase in JNK activity at 0.5 h followed by a remarkable decrease, and another episode of increase at 6 h was noted. ERK activity was prominently suppressed by 0.5 h, followed by a gradual return to normal level. p38MAP activity was constitutively increased at 18 h following treatment. Treatment with 20 μg/ml ANE resulted in similar fluctuation in JNK activities. However, a persistent suppression of ERK and a progressive increase of p38MAP activity were induced by such treatment. The electrophoretic mobility shift assay illustrated that the NF-κB activity were regulated by ANE. Both 10 and 20 μg/ml ANE treatment activated NF-κB for ∼2 and ∼4 folds, respectively, at 0.5 h. The activities were maintained in plateau phase during 1 h - ∼6 h. Afterward, another increase in NF-kB activity for ∼4 - ∼9 folds, respectively, was noted. Supershift assay indicated that the activated NF-κB components were mainly p50 and p65, with p68 (RelB) and p75 (c-Rel) as minor ones. PDTC, a NF-κB inhibitor, substantially blocked the NF-κB activities induced by ANE. This study is the first report denoting that ANE affects multiple signaling systems in oral keratinocyte that could be the molecular basis for oral pathogenesis. Abrogation of NF-κB activity may intercept the genesis of areca-associated oral carcinogenesis.